ASTM G209-12
(Practice)Standard Practice for Detecting mu-phase in Wrought Nickel-Rich, Chromium, Molybdenum-Bearing Alloys
Standard Practice for Detecting mu-phase in Wrought Nickel-Rich, Chromium, Molybdenum-Bearing Alloys
SIGNIFICANCE AND USE
4.1 These test methods describe laboratory tests to determine the presence of mu-phase in Wrought Nickel-Rich, Chromium, and Molybdenum-Bearing Alloys through comparison of microstructure observed for etched metallographic specimens to a glossary of photomicrographs displaying the presence and absence of mu-phase in the microstructure. The presence of mu-phase in the microstructure may significantly reduce the corrosion resistance, strength, toughness and ductility of Wrought Nickel-Rich, Chromium, and Molybdenum-Bearing Alloys.
SCOPE
1.1 This practice incorporates etching and metallographic examination of Wrought Nickel-Rich, Chromium, Molybdenum-Bearing Alloys such as, but not limited to, UNS N06686 and UNS N10276.
1.2 Microstructures have a strong influence on properties and successful application of metals and alloys. The presence of mu-phase in the microstructure may significantly reduce the corrosion resistance of Wrought Nickel-Rich, Chromium, and Molybdenum-Bearing Alloys.
1.3 This practice may be used to determine the presence of mu-phase in Wrought Nickel-Rich, Chromium, and Molybdenum-Bearing Alloys through comparison of microstructure observed for etched metallographic specimens to a glossary of photomicrographs displaying the presence and absence of mu-phase in the microstructure.
1.4 The values stated in SI units are to be regarded as the standard. Other units are given in parentheses for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: G209 − 12
StandardPractice for
Detecting mu-phase in Wrought Nickel-Rich, Chromium,
Molybdenum-Bearing Alloys
This standard is issued under the fixed designation G209; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E1268Practice for Assessing the Degree of Banding or
Orientation of Microstructures
1.1 This practice incorporates etching and metallographic
G193Terminology and Acronyms Relating to Corrosion
examination of Wrought Nickel-Rich, Chromium,
Molybdenum-BearingAlloys such as, but not limited to, UNS
3. Terminology
N06686 and UNS N10276.
3.1 Definitions:
1.2 Microstructures have a strong influence on properties
3.1.1 The terminology used herein, if not specifically de-
and successful application of metals and alloys. The presence
fined otherwise, shall be in accordance with Terminology
ofmu-phaseinthemicrostructuremaysignificantlyreducethe
G193. Definitions provided herein and not given in Terminol-
corrosion resistance of Wrought Nickel-Rich, Chromium, and
ogy G193 are limited only to this practice.
Molybdenum-Bearing Alloys.
3.1.2 For metallographic definitions used in this practice,
1.3 This practice may be used to determine the presence of
refer to Terminology E7.
mu-phase in Wrought Nickel-Rich, Chromium, and
3.1.3 For evaluation of inclusions, secondary phases and
Molybdenum-Bearing Alloys through comparison of micro-
banding, if desired, refer to Practices E1245 and E1268.
structure observed for etched metallographic specimens to a
3.2 Definitions of Terms Specific to This Standard:
glossary of photomicrographs displaying the presence and
3.2.1 mu-phase (µ), n—rhomohedral phase which may oc-
absence of mu-phase in the microstructure.
cur in Nickel-Rich, Chromium, Molybdenum-Bearing Alloys
andmayoccurascoarse,irregularplatelets,whichformathigh
1.4 The values stated in SI units are to be regarded as the
temperature.
standard. Other units are given in parentheses for information
only.
4. Significance and Use
1.5 This standard does not purport to address all of the
4.1 These test methods describe laboratory tests to deter-
safety concerns, if any, associated with its use. It is the
mine the presence of mu-phase in Wrought Nickel-Rich,
responsibility of the user of this standard to establish appro-
Chromium, and Molybdenum-Bearing Alloys through com-
priate safety and health practices and determine the applica-
parison of microstructure observed for etched metallographic
bility of regulatory limitations prior to use.
specimens to a glossary of photomicrographs displaying the
2. Referenced Documents
presence and absence of mu-phase in the microstructure. The
presence of mu-phase in the microstructure may significantly
2.1 ASTM Standards:
reduce the corrosion resistance, strength, toughness and duc-
D1193Specification for Reagent Water
tility of Wrought Nickel-Rich, Chromium, and Molybdenum-
E3Guide for Preparation of Metallographic Specimens
Bearing Alloys.
E7Terminology Relating to Metallography
E1245Practice for Determining the Inclusion or Second-
5. Sample Preparation and Etching
Phase Constituent Content of Metals byAutomatic Image
5.1 Sectioning:
Analysis
5.1.1 The selection of test specimens for metallographic
1 examination is extremely important because, if their interpre-
This test method is under the jurisdiction of ASTM Committee G01 on
Corrosion of Metals and is the direct responsibility of Subcommittee G01.05 on tationistobeofvalue,thespecimensmustberepresentativeof
Laboratory Corrosion Tests.
the material that is being studied and shall be per location E
Current edition approved May 1, 2012. Published May 2012. DOI: 10.1520/
(longitudinal section perpendicular to rolled surface) for plate
G0209–12.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Manning, Paul E., Ph.D., Metallographic Preparation of 686 Etching
the ASTM website. Specimens, Haynes International, Inc., Kokomo, IN, 2011.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G209 − 12
and sheet and per location G (radial longitudinal section) for mounts.Phenolicmountsareconvenientwhentimeconstraints
rod and bar per Fig. 1 (Guide E3).The intent or purpose of the do not permit an overnight cold-setting operation.
metallographic examination will usually dictate the location of
5.4 Fine Grinding and Polishing—Rotating discs flushed
the specimens to be studied. For rod and bar test specimens
with running water are recommended with successively finer
specifically, samples are taken from ¼-diameter per location G
grit papers of 220, 320, 400, and 600 grit SiC. (A light to
as seen in Fig. 1. Triplicate test specimens shall be evaluated
medium amount of pressure is exerted on the specimen to
for determination of the presence of mu-phase.
minimize the depth of deformation). Best results are obtained
5.1.2 Cut the specimen to a convenient size using any of
on the 600 SiC paper by grinding the specimen twice.
various types of silicon carbide, diamond, boron carbide or
Specimens shall be rotated 90 degrees after each step until the
other carbide cutoff blades. Deformation damage can be
abrasive scratches from the preceding grit have been removed.
minimized by using thin cutoff wheels 0.78 mm ( ⁄32 in.) thick
In each step, the grinding time shall be increased to twice as
asopposedto1.58mm( ⁄16in.).Nevercutdry.Useofadequate
long as that required to remove previous scratches. This
water coolant is desired to reduce the amount of disturbed
ensures removal of disturbed metal from the previous step.
metal created, in part, from frictional heat during this phase of
Considerable care shall be used in the fine grinding stage to
preparation. The original microstructure of a specimen may
prevent the formation of artifacts. See Guide E3 for automated
also be radically altered, (at least superficially, on the cut
method.
surface)duetometallurgicalchangesifanexcessiveamountof
5.5 Rough Polishing—The specimen shall be washed and,
frictional heat is generated.
preferably, ultrasonically cleaned to ensure the complete re-
5.2 Coarse Grinding—Use a 120 grit silicon carbide (SiC)
movalofsiliconcarbidecarryoverfromthefinegrindingstage.
wet-belt or disk grinder and light contact pressure to obtain a
Anaplesstypeclothshallbechargedwith9-µmdiamondpaste,
plane surface free from deep grooves. In addition to producing
andwatermaybeusedasthelubricant.Thespecimenismoved
a flat surface, this procedure removes burred edges or other
countertothedirectionoftherotatingpolishingwheelfromthe
mechanical damage which may have occurred during section-
center to the outer periphery around the entire lapping surface.
ing.
Heavy pressure is used with diamond abrasive techniques to
5.3 Mounting—To ensure flatness, and facilitatehandling,it gainthemaximumcuttingrate.Attheconclusionofthisstage,
is recommended that specimens be mounted in phenolic, the specimen shall again be cleaned to remove any diamond
acrylic or cold-setting epoxy resins. Epoxy resins involve the polishing residue remaining in pinholes, cracks, and cavities.
blending of a liquid or powder resin in a suitable hardener to
5.6 Vibrator Polishing:
initiate an exothermic reaction to promote hardening and
5.6.1 Semi-final and final polishing operations on a major
curing at room temperature.This usually requires an overnight
portion of metallographic specimens may be completed on
operation.However,anadvantageofepoxyisthatthemountis
vibratorypolishingunits.Anylonpolishingclothusingaslurry
semitransparent and permits observation of all sides of the
of 30 g of 0.3 µm alumina polishing abrasive and 500 mL of
specimen during each phase of the preparation. (The advan-
distilled or deionized water are recommended for this opera-
tages and use of acrylic mounting resin are similar to epoxy.)
tion.Additionalweightintheformofastainlesssteelcapmust
Compression molding techniques may be used with phenolic
be placed on the specimen. The suggested weight to achieve a
powders to produce the standard 31.7-mm (1¼-in.) diameter
satisfactory polish in 30-60 min on a 31.7 mm (1¼-in.)
diameter mount is 350 g.
5.6.2 Other methods of final polishing may be utilized, for
exam
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